Hypopigmentary conditions include vitiligo, and reduced pigmentation due to surgery or other trauma to the skin. Melanocytes are the cells that produce the pigment in the skin and deliver it to the surrounding keratinocytes. Those cells are very fragile and are easily destroyed in case of trauma or surgery (including some laser treatments) leading to hypopigmented scars that can cause psychological discomfort especially in highly pigmented patients. Vitiligo is an acquired cutaneous disorder of pigmentation, with a 0.5% to 2% incidence worldwide, without predilection for sex or race. The clinical presentation is characterized by well circumscribed, white cutaneous macules. Clinical presentation includes segmental vitiligo with a unilateral pattern of the lesions, focal vitiligo characterized by a limited number of depigmented macules without segmental distribution, universal vitiligo which involved complete or almost complete body surface area and generalized vitiligo, the most common type, characterized by a bilateral and symmetrical distribution of the lesions. Individuals affected by vitiligo have a vast reduction of quality of life caused by the colour contrast between healthy pigmented skin and the depigmented vitiligo patches which give the patients psychological problems. Physicians have a large variety of therapeutic approaches (medical (including phototherapy, depigmenting therapies and camouflaging) and surgical) but up to now no treatment provides truly satisfactory results. Other acquired hypopigmentary disorders such as post-surgical leukoderma, are also very frequent and in most cases, remain also challenging to treat.
Hyperpigmentary conditions are very common and come from many origins. Melasma (also called pregnancy mask) is very frequent among young women and is not only related to pregnancy. Its treatment remains challenging especially when the pigment is located in the dermis. Among other types of hyperpigmentation, lentigo senilis (age spots) are also very frequent. Treatment with lasers is effective but remains costly. Other conditions leading to hyperpigmentation are numerous such as freckles, post-inflammatory pigmentation, café-au-lait spots, and acquired brachial pigmentation, just to cite the more frequent.
Melanoma is one of the most deadly cancers. It is generally resistant to radiotherapy and chemotherapy can only provide in the best cases a few additional months of survival. Although used with success in several other cancers, including leukemia or solid cancers such as some breast cancers, retinoic acid (RA) or its derivatives are also ineffective in treating melanoma.
A better understanding of pathways regulating the proliferation of melanoma cells is required to develop efficient strategies to treat this burden on public health. MITF, a transcription factor well known to play a key role in regulating melanogenesis, has been shown to control the proliferation of melanoma cells by directly regulating the p21 promoter (1). Concomitantly it has been shown that MITF acts as an anti-proliferation factor that is down-regulated by B-RAF signaling (2).
SOX9 is a transcription factor that is predominantly reported to be involved in developmental biology. SOX9 has a key role in sexual determination and chondrogenesis and mutations in its encoding gene can lead to campomelic dysplasia and sex reversal (3,4). However there are increasing reports showing the active role of SOX9 in adult tissues such as heart; kidney or brain (5-7).